Conveyor systems for moving objects between stations in a manufacturing environment or for accumulating and distributing products in a warehouse operation are well known in the art. Such conveyor systems provide upwardly exposed conveying surfaces, such as rollers, positioned between guiding side rails. The rollers are powered by controllable motors to move objects placed on top of them along a track defined by the rails.
Assembly of conveyor systems is facilitated by the use of “conveyor sticks” comprised of short sections of rollers and guide rails, which are connected together to form the final conveyor system. This modular construction also simplifies changes in the layout of the conveyor system.
The conveying surface of each conveyor stick may be broken up into one or more zones, each associated with a sensor for detecting the presence of an object on the conveyor at the zone. A control circuit communicates with each zone and sensor via a number of cables to control the zones so as to accomplish a number of standardized tasks.
One task is that of “accumulation” in which the control circuit for a given zone operates its rollers when the sensor, in an upstream zone, indicates an object is at that zone and the sensor of a “downstream” zone indicates that no object is in that downstream zone. This logic causes the conveyor zones to move objects along to fill all zones with objects.
In a “slug release” operation, each control circuit in a defined release zone operates its rollers if its sensor indicates an object is present and no object is in the downstream zone from the defined release zone. This logic causes the emptying of a predefined section of the conveyor, typically to a downstream portion.
A third mode of operation is “singulation release” in which a single object at a time is unloaded from the conveyor system 10. Each upstream control circuit operates its rollers to move its objects downstream one zone.
In order to perform these tasks, the control circuit for each conveyor stick must communicate in a limited fashion with the control circuits (or at least the sensors) of the upstream and downstream conveyor sticks. This is done by cabling between control cards or sensors of the conveyor stick, typically within one of the side rails.
Advantageously, the conveyor system as described operates without the need for a central controller, for example, such as may require several dedicated I/O points for each zone together with the need to route a large number of wires through the cable raceways between the conveyors and the central controller. By eliminating the need for this wiring, the conveyor sticks can be easily assembled or reconfigured. Nevertheless, the lack of central control makes the conveyor system relatively hard to reconfigure requiring, for example, settings to being manually adjusted on each controller board when delay times and conveyor speeds are changed. Further, lack of centralized communication between components of the conveyor system makes it difficult to detect and report conveyor system problems such as motor failure or material jamming.